If you’re an asphalt shingle roof homeowner, you’ve definitely been worried about residential roof shrinkage. You’ve likely found a blog discussing how it damages and reduces your roof’s lifespan. Unfortunately, these are all true, but it’s a much more common occurrence on commercial roofs than residential ones.

Before you dive deeper into this topic with your ever-reliable Calgary AB roofing company with decades of experience, let’s start at the beginning. What is roof shrinkage? What causes it? Michael King Roofing has a great explanation about it below.

What is roof shrinkage?

For starters, most homeowners are not even aware of what roof shrinkage is. It is a common misconception that roof shrinkage is the actual shrinking of your roofing materials over time. Instead, it refers to the membrane that coats your roofing materials shrinking and ultimately wearing away. This membrane, known as the ethylene propylene diene monomer (EPDM), is the membrane that works to protect your home from significant damage caused by extreme temperatures, weather and other damage caused by objects to your roof. Over time, this membrane shrinks and can lead to many problems if left without repair. Some issues are cracks, tears, and ridges in the roofing materials, to name a few.

Why does roof shrinkage occur?

A number of things can cause roof shrinkage.

Inadequate manufacturing or application of membrane and materials

The EPDM membrane requires several careful steps to develop and apply it to the roofing materials accurately. If there is a lack of quality in the production of the membrane at any point, the membrane’s durability can be drastically decreased, and its protection to your home is weak. If in fact the quality of the membrane is fine, but the oil is not mixed correctly before applying it to the roofing materials, the membrane won’t have the necessary flexibility to function correctly.

Extreme wear and tear in harsh environments

The membrane should be able to withstand general aging of the material. However, in climates with harsher climates and environments, the membrane may wear more quickly. Constant exposure to this and UV exposure drastically decreases the membrane’s lifespan.

The content above talked about numerous reasons why residential roof shrinkage (or at least material shrinkage) occurs. They used inadequate materials, accelerated wear and tear, and poor roof design considerations incompatible with both EPDM and modified bitumen (the most common materials to suffer from residential roof shrinkage).

Is there any way to prevent this from happening? Yes, there is. If you can install flat roofs efficiently, you prevent any possible untoward damages in the future. In addition, you require minimal maintenance too. To make sure commercial property owners have installed their flat roofs efficiently and prevent possible roof shrinkage, This Old House has some great instructions to help you go about it.

The Right Way Contractors Build Flat Roofs To Prevent Residential Roof Shrinkage

The Importance of Building it Right

Sheathing goes down quickly on a roof that isn’t sloped and thus provides some footing. But the horizontal lines of this 8 ½-by-13-foot flat roof section at the Cambridge TV project house, make it vulnerable to heavy snow and pooling rainwater, which is why it must be built to last.

Frame the Roof

“The most important thing to know about a flat roof,” says Tom, “is that it’s not flat.” To prevent water from pooling and eventually invading the home, flat roofs are always built on a slight incline—at least 1⁄8 inch per foot. Many slope in several directions, like squashed hip roofs, toward scupper holes that connect to downspouts.

Sheathe With Plywood

On top of the framing goes 5⁄8-inch plywood sheathing with a 1⁄8-inch gap at all the joints to allow for expansion and contraction.

Screw Down Underlayment

The sheet-rubber roofing material that Tom is using requires a substrate called iso board—½-inch-thick rigid foam (made of polyisocyanurate) with a special fiberglass backing. The iso board (a flat version of the same material he orders custom-fitted for larger roofs) cuts easily with a utility knife and anchors to the plywood sheathing with screws and large galvanized steel washers. It provides a soft, protective base for the rubber. Tom makes sure to stagger the joints and to fit the pieces tightly against each other, as iso board doesn’t expand and contract like plywood. (Continued)

You’ve definitely made a connection between modified bitumen and asphalt shingle roofing. Aside from its heat-welding installation, the two materials use asphalt and an organic base to provide roofing. Can residential roof shrinkage happen with asphalt shingle roofs?

The truth: yes, it can. However, it is highly unlikely to happen unless your Calgary AB weather is extreme for at least an entire month. That means a sudden drop and rise in temperatures. However, it is possible, but it can rarely happen unless your asphalt shingle roof is nearing the end of its lifespan. Prugar Consulting has a great post about asphalt shingle residential roof shrinkage. Read an excerpt below.

Residential Roof Shrinkage: Characteristics of Aging in Asphalt Roofs

The following is the last of five lists of characteristics exhibited by aging asphalt shingles:


Shrinkage is the shortening of the width and/or the depth of the shingle tab as the moisture and the petroleum or other soluble base evaporate from it. Shrinkage is due to the normal aging and weathering of the asphalt materials. Shrinkage is commonly increased by the exposure of the shingle to excessive heat from an inadequately ventilated attic or from a southern exposure.

Wear And Granule Loss At Edges Of Shingle Tabs

Granule loss at the edges of shingles tabs is commonly the result of normal aging and weathering of the asphalt, which degrades the bond strength, and the dislodging of the granules along the edge through abrasion by normal foot traffic.


Shingle defects appear as irregular shaped, but sometimes circular shaped, areas of granule loss where the asphalt coating or the shingle mat is exposed due to the granules not bonding adequately to the asphalt coating or the asphalt coating not bonding adequately to the fiberglass mat. The inadequate bonding is commonly due to the poor application of the asphalt or the localized contamination of the shingle mat or the asphalt coating that bonds the granules to the shingles during the manufacturing process. Normal aging and weathering loosens the inadequately adhered granules leaving a small area of fiberglass mat or asphalt exposed.

At this point, it’s clear: the solution to prevent possible commercial or residential roof shrinkage is to call on a trusty roofing company in Calgary AB that you can depend on. If you have yet to find one, you can count on No Payne Roofing’s experts with more than 10 years of experience providing quality service. Contact us today!